STING, also known as transmembrane protein 173 (TMEM173) and MPYS/MITA/ERIS, is a protein that in humans is encoded by the TMEM173 gene. STING has been shown to play a role in innate immunity. STING induces type I interferon production when cells are infected with intracellular pathogens, such as viruses, mycobacteria and intracellular parasites. Type I interferon, mediated by STING, protects infected cells and nearby cells from local infection in an autocrine and paracrine manner. The STING pathway is a pathway that is involved in the detection of cytosolic DNA.
The STING signaling pathway is activated by cyclic dinucleotides (CDNs), which may be produced by bacteria or produced by antigen presenting cells in response to sensing cytosolic DNA. Unmodified CDNs have been shown to induce type I interferon and other co-regulated genes, which in turn facilitate the development of a specific immune response (see, e.g., Wu and Sun, et al., Science 2013, 339, 826-830). WO 2015/077354 discloses the use of STING agonists for the treatment of cancer.